There is an increasing number of consumer products being operated by rechargeable cells, such as nickle-cadmium cells. Rechargeable batteries are manufactured in sizes corresponding to many of the non-rechargeable batteries, e.g. AA, C, D, and 9-volt sizes, with the result that consumers may substitute a rechargeable battery for a non-rechargeable battery and vice versa.
Many consumer appliances are now equipped with internal circuitry and sold with charging transformers so that rechargeable batteries may be charged in place in the appliance. Many of these appliances also accept primary batteries which cannot be recharged and should not be subjected to recharging. As a result the need exists for a method of using both primary and rechargeable batteries interchangeably but without charging the primary batteries.